Well production methods and apparatus



Sept. 20, 1966 p LEBQURG ET AL 3,273,639

WELL PRODUCTION METHODS AND APPARATUS Filed July 27, 1960 IN V EN TORJ ATTORNEY Patented Sept. 20, 1966 3 273,639 WELL PRODUCTION METHODS AND APPARATUS Maurice P. Lebourg and John T. Dewan, Houston, Tex., assignors to Schlumberger Well Surveying Corporation, Houston, Tex., a corporation of Texas Filed July 27, 1960, Ser. No. 45,694 4 Claims. (Cl. 166-4) This invention relates to methods and apparatus for dual well completion and, more particularly, pertains to new and improve-d methods and apparatus for accurately positioning or locating a perforator in one of a number of tubular members traversing a well drilled into the earth.

In one type of well completion presently in practice and commonly known as multiple well completion, two or more strings of small diameter tubing are disposed in a well bore to extend respectively to various production zones at different levels relative to the earths surface. The tubing strings are cemented in the well bore, thereby forming individual casings or well strings.

The completion practice generally has been to pass successively through each string of tubing, a logging tool which provides a surface record or log of natural or induced formation radioactivity (or both) and of the position of tubing collars as a function of depth. Next a well completion tool which includes a tool for locating collars and perforating apparatus is successively employed in each string of tubing to complete the same by placing the respective formations in fluid communication with the respective strings of tubing. The collar locating tool in the well completion tool is used to provide a surface record or log of the position of the tubing collars as a function of depth. Therefore, in the completion described above, in a given string of tubing, the one log of formation radioactivity and position of tubing collars is correlated with the collar log of the completion tool, while the completion tool is in the string of tubing. Thus, the completion tool is located at a position adjacent the collar closest to and below the desired formation by means of the collar log obtained by the completion tool. Thereafter, with this located collar as a fixed reference point, the completion tool is raised to the depth of the formation zone and the zone perforated.

It will be appreciated that this perforating depth control system eliminates many sources of error in locating the completion tool. This is because the desired formation zone will lie between fixed collars in the string of tubing where the length of tubing is standard (about 30 feet in length) and, hence, the depth recorder for the cable length is only used to position the completion tool a given number of feet from the collar reference point. It will, therefore, be appreciated that the accuracy with which the completion tool is located is extremely good.

In multiple well completions, as above described, it will be appreciated that it was necessary to obtain a collar log and a radioactivity log of the formations for each string of tubing to correlate the selected formations along the length of the well bore with the completion tool in each string of tubing. This procedure involves a considerable amount of rig time in running the separate logging operations for each string of tubing and thus increases the cost of the well completion.

By means of the present invention, the well completion is simplified by eliminating the need for logging each string of tubing with radioactivity apparatus so that only one string of tubing is logged with radioactivity apparatus and all other strings of tubing may then be completed by use of the completion tool. Hence, rig time is shortened since, immediately after logging the one string of tubing, all of the tubings may be completed.

Accordingly, it is an object of the present invention to provide new and improved methods of locating a perforating apparatus in one of a number of strings of tubing in a well bore with a minimum of logging operations.

This and other objects of the present invention are obtained by deriving, simultaneously, in a primary string of tubing in a Well bore, a record of the location of the characteristics or parameters of the adjacent earth formations, a record of the location of the collars in the primary string of tubing, and a record of the location of prescribed radioactive markers or anomalies in each adjacent string of tubing. The secondary string or strings of tubing may then be completed by lowering a perforating apparatus and anomaly detector which derive a record of the collars in the secondary string of tubing and also a record of a magnetic anomaly which is specifically related to the location of the radioactivity anomalies in the second tubing string. The magnetic anomaly is correlated with the radioactivity anomaly and, hence, the tubing collars in the necessary string of tubing .are correlated with respect to the formation characteristics obtained in the log of the primary string of tubing. The novel features of the present invention are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages thereof, may best be understood by way of illustration and example of certain embodiments when taken in conjunction with the accompanying drawings in which:

FIG. 1 illustrates a borehole containing three strings of tubing respectively extending to various depths from the earths surface;

FIG. 2(ac) is a schematic representation of a log obtained by radioactivity devices and a collar locating device in the longest string of tubing;

FIG. 3 is a schematic representation of a log obtained by a collar locating device in the next longest string of tubing; and

FIG. 4 is a schematic representation of a log obtained by a collar locating device in the shortest string of tubing.

In FIG. 1 of the drawing, a borehole 10 is shown traversing zones of earth formations 11-17 and disposed therein are a primary string of tubing 18 and secondary strings of tubing or casing 19 and 20. The primary string of tubing 18 extends between the earths surface to the greatest depth at which a production zone or level 16 is located. A secondary string of tubing 19 is coextensive and adjacent to the primary string of tubing 18 and extends downwardly to an intermediate depth where zone 14 is located. The remaining secondary string of tubing 20 extends to the uppermost depth where zone 12 is located.

Each string of tubing 18-20 which are generally identical in length and having threaded ends (not shown), the sections of tubing being coupled to one another *by threaded collars, shown as short, heavy lines are identified by the numerals 18a, 19a and 20a for the respective strings of tubing 18-20. A section of tubing normally is about 30 feet in length; hence, a great many sections of pipe are usually employed to extend a string of tubing to a depth which may typically be many thousands of feet. The strings of tubing 18-20 generally are of smaller diameter, for example, 2 /2", and are cemented in place by a column of cement 23 in the borehole 10, so that they, in effect, form individual well strings. Of course, it will also be appreciated that a plurality of strings of tubing can also be disposed in a cased bore and suitably packed off from one another.

In accordance with the present invention, the secondary strings of tubing 19 and 20 are provided with marker devices to produce magnetic and radioactivity anomalies. Such devices may, for example, he specially prepared includes sections of tubing pup joints (shown as long, heavy lines and identified by the numerals 29 and 30) for the respective strings of the tubing 19 and 20. These pup joints are conveniently about three feet in length and may be constructed of, say, an alloy of nickel and copper, commonly referred to as Monel, which is relatively non-magnetic as compared to the steel in the tubing sections. It 'Will, however, be appreciated that the pup joints may be of ordinary steel composition since the short length of the joints and the indications obtained at the coupling of the pup joint to the tubing string will readily identify the pup joint. Hence, a collar locator device, which res-ponds to magnetic anomalies in a string of tubing, will respond to the anomaly at the upper and lower ends of a pup joint to develop spaced indications of the ends of the pup joint. A suitable collar locating device (hereinafter sometimes referred to as CCL), for example, may be of the type described in Patent No. 2,558,427.

The outer surface of each pup joint is coated with a radioactive material such as carno-tite by using, for example, an epoxy binder, so that the pup joint creates a radioactive anomaly in the corresponding string of tubing. As will become apparent from the discussion to follow, other types of radioactive marking can be employed. For example, only the ends of a pup joint can be coated or an annular tubing insert, including radioactive material, can be disposed between the threaded connection between pipes.

Hence, as shown in FIG. 1, primary tubing string 18 has collars 18a along its length while secondary tubing strings 19 and 20, in addition to respectively having collars 19a and 20a, respectively have pup joints 29 and 30 which provide radioactive and magnetic markers.

With the well containing the strings of tubing 18-20, as above described, only the primary string 18 need be logged for indications of the earth format-ions since, by means of the present invention, locations in the secondary strings of tubing 19 and 20 may be correlated with respect to tubing string 18 by collar indications which are routinely obtained with a perforating apparatus.

In a typical well completion, in accordance with the present invention, a logging tool (shown in dashed lines 24), which includes a collar locator device 24a, 21 conventional gamma ray logging device 24b and a conventional neutron logging device 24c, is introduced to the primary string of tubing 18 to obtain a complete log of the earth formations relative to the collars of the primary string of tubing. Further explanation of these conven tional devices may be found on pages 2908-2910 of the Composite Catalog of Oil Field Equipment and Services, 23rd revision, 19581959 edition. Tool 24 may be lowered by means of a cable 26 and winch (not shown), while a measuring wheel 27 and recorder 28 at the surface are employed to obtain indications of depth and to provide a record of the responses obtained by the tool.

The gamma ray logging device 24b, which delineates or determines the shale zones in the earth formation, typically produces a response, as shown in FIG. 2a, wherein the displacement of the curve to the left of the normal shale base line-curve 1111, as shown by numerals 12a, 14a, 16a, would indicate non-shale zones 12, 14, and 16, which are typically potential producing sands. Similarly, the neutron logging device 24c produces a record, as illustrated in FIG. 2b, as a function of depth, the neutron device being sensitive to the presence of hydrogen. Generally, the sandy zones 12, 14 and 16, containing lower hydrogen concentrations than shale, cause a displacement of the curve to the right of the base line 11b, as indicated by the numerals 12b, 14b, 16b. Either the gamma ray log (GRL) or neutron log (NL) may be correlated with previous open hole logging records taken by other investigating methods, such as electrical, sonic or induction logs, to more particularly correlate or identify zones of interest. The CCL detects the locations of collars 18a to produce indications (voltage undulations 4 with respect to a base value), such as indicated by the numeral 18b (FIG. 20) for each of the collars in the string of tubing.

Therefore, to bring in production from zone 16, a perforator 25 and collar locating device 24a (shown in dashed lines in tubing string 19) is introduced in the primary string of tubing 18 and lowered until the CCL indicates a collar 18a adjacent to zone 16 has been reached. Since the log of the collars and radioactivity as a function of depth will indicate the number of feet between the adjacent collar and the formation zone 16, perforator 24 is then positioned by measuring the numer of feet with the cable wheel 27 as the perforator is moved this relatively short distance to the location of the zone, and the zone 16 perforated. Thus, it will be appreciated that the zone 16 may be perforated with extreme accuracy on the depth control of the perforating apparatus because the location is only a short interval from a fixed collar;

By means of the present invention, the pup joints 29 and 30 in adjacent secondary strings of tubing 19 and 20, which have radioactive coatings, will affect the radioactivity log. In the case of joints coated entirely with carnotite, the produce an indication of the location of the pup joints in the adjacent strings, as indicated by the numerals 29a and 30a in FIG. 2a.

To bring in production through the secondary strings of tubing 19 and 20, or to perforate for testing or remedial purposes, only a perforating apparatus 25 and CCL 24a are required. For example, as the perforator and CCL are lowered through a secondary string of tubing 19, the CCL will develop signals 2% and 19b (FIG. 3) respectively, in response to the pup joint 29 and the collars 19a. The respective signals 29b for the pup joint, as shown in FIG. ,3, are correlated with the top and bottom of the pup joint 29 at a spacing representative of the longitudinal dimension of the joint and, hence, it is easily distinguishable from the collar signals 19b. Consequently, these anomalies may be independently identified and located relative to the casing collars in the string of tubing.

The magnetic indications 29b of the pup joint 29 in a secondary string of tubing 19 are correlative with the radioactivity indications 29a (FIG. 2a) obtained in the primary string of tubing 18. Hence, by aligning indications 29a and 2% relative to one another, the spacing of zone 14 on the log of FIGS. 2a, relative to the collar 19b on the log of FIG. 3 closest to the zone may be very accurately located and the perforating apparatus accurately positioned at zone 14, as above described.

Each remaining secondary string of tubing, such as tubing 20 may be perforated at an accurate depth location in a manner as described above with respect to tubing string 19, by correlating the magnetic anomaly with the corresponding radioactive anomaly on the primary radioactivity log.

It will be appreciated that the perforating apparatus for strings of tubing 19 and 20 is of the type which may be oriented so as to perforate only the desired string of tubing of the multiple strings of tubing, for example, a 'y'y orienting perforator which is currently available. Further explanation of the 'y'y orienting perforator may be found in the article entitled Perforating of Multiple Tubingless Completions in the May, 1960 issue of Journal of Petroleum Technology. Moreover, it should be noted that the present invention may be practiced with other varients such as an irregular length of regular pipe doped with radioactive isotope of suitable half-life.

Another example of a radioactivity type of marker would be to mark the pup joint with a strong thermal neutron absorber such as boron to give an indication on a neutron log obtained with a neutron-gamma or neutronneurton logging device 24c run in primary string 18.

While a particular embodiment of the present invention has been shown and described, it is apparent that gamma ray log (FIG. 2a) will respond'tochanges and modifications may be made without departing from this invention is its broader aspects and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

We claim:

1. A method for completion of one string of tubing relative to a coextensively extending string of tubing in a well bore comprising the steps of: disposing a first string of tubing coupled by collars in a well bore to the greatest depth at which production is expected; disposing a second string of tubing coupled by collars in the well bore wherein said second string of tubing includes a section of pipe having characteristic, identifiable magnetic anomalies distinct from magnetic anomalies caused by collars in said second string of tubing and a characteristic radioactivity anomaly in a known location in the second string of tubing relative to said magnetic anomalies; logging the earth formations traversed by said first string of tubing with radioactivity anomaly detecting means to obtain indications of the radioactivity of the traversed earth formations and indications of the characteristic radioactivity anomaly in said second string of tubing as a function of depth, logging the second string of tubing with magnetic anomaly detecting means having attached thereto a perforator and obtaining indications of collar couplings and said identifiable magnetic anomalies, and positioning said perforator at a desired depth relative to said identifiable magnetic anomalies and a selected collar coupling.

2. A method for completion of one string of tubing relative to a coextensively extending string of tubing in a Well bore comprising the steps of: disposing a first string of tubing coupled by collars in a Well bore to the greatest depth at which production is expected; disposing a second string of tubing coupled by collars in the well bore wherein the string of tubing includes a section of pipe having a characteristically different length as compared to other pipe lengths to develop characteristic magnetic anomalies identifiable from collar couplings and having a characteristic radioactivity anomaly; logging the earth formations traversed by the first string of tubing with radioactivity anomaly detecting means to obtain indications of the radioactivity of the traversed earth formations and indications of the characteristic radioactivity anomaly in the second string of tubing as a function of depth; and logging the second string of tubing with magnetic anomaly detecting means to obtain indications of collar couplings and magnetic anomalies of said pipe section as a function of depth.

3. A method for completion of one string of tubing relative to a coextensively extending string of tubing in a well bore comprising the steps of: disposing a first string of tubing coupled by collars in a well bore to the greatest depth at which production is expected; disposing a second string of tubing coupled by collars in the well bore wherein the string of tubing includes a section of pipe having a characteristically different length as compared to other pipe lengths to develop characteristic magnetic anomalies identifiable from collar couplings and having a characteristic radioactivity anomaly; logging the earth formations traversed by the first string of tubing with radioactivity anomaly detecting means to obtain indications of the radioactivity of the traversed earth formations and indications of the characteristic radioactivity anomaly in the second string of tubing as a function of depth; and lowering into the second string of tubing a perforator and magnetic anomaly detecting means to obtain indications of collar coupling and magnetic anomalies of said pipe section as a function of depth, and locating said perforator at a desired depth relative to said characteristic magnetic anomalies of said pipe section.

4. A method of locating the perforating depth in the second of two collar coupled well strings in a well bore wherein the second well string includes a length of well pipe having a characteristically different length as compared to other pipe lengths and has a characteristic radioactivity -anomaly, and Where the first well string extends downwardly in the well bore beyond the location of the aforesaid length of well pipe, comprising the steps of: logging the earth formations traversed by the first of the two well strings with radioactivity anomaly detecting means to obtain indications of the radioactivity of the traversed earth formations and indications of the characteristic radioactivity anomaly in the second well string as a function of depth thereby correlating the earth formations radioactivity relative to said characteristic radioactivity anomaly, and lowering into the second well string a perforator and a magnetic anomaly detecting means to obtain indications of collar couplings as a function of depth and thereby permit a determination of the depth of the pipe length having a characteristically different length, and locating the perforator in the second well string at a desired depth relative to said short length of pipe.

References Cited by the Examiner UNITED STATES PATENTS 2,228,623 1/1941 Ennis 166-35 2,246,542 6/1941 Smith 166-35 2,309,835 2/1943 Fearon 16635 2,320,890 6/1943 Russell 16666 X 2,352,993 7/1944 Albertson 25083.6 2,370,909 3/1945 Martin 166- 35 2,446,640 8/1948 Davis 166-35 2,476,137 7/1949 Doll 16635 2,631,671 3/1953 Krasnow et al. 166-35 2,842,852 7/1958 Tanguy 166-4 X 2,998,068 8/1961 True 16655 3,019,841 2/1962 Ternow 166-4 CHARLES E. OCONNELL, Primary Examiner. BENJAMIN BENDETI, Examiner. D. C. BLOCK, D. H. BROWN, Assistant Examiners. 

2. A METHOD FOR COMPLETION OF ONE STRING OF TUBING RELATIVE TO A COEXTENSIVELY EXTENDING STRING OF TUBING A WELL BORE COMPRISING THE STEPS OF: DISPOSING A FIRST STRING OF TUBING COUPLED BY COLLARS IN A WELL BORE TO THE GRATEST DEPTH AT WHICH PRODUCTION IS EXPECTED; DISPOSING A SECOND STRING OF TUBING COUPLED BY COLLARS IN THE WELL BORE WHEREIN THE STRING OF TUBING INCLUDES A SECTION OF PIPE HAVING A CHARACTERISTICALLY DIFFERENT LENGTH AS COMPARED TO OTHER LENGTHS TO DEVELOP CHARACTERISTIC MAGNETIC ANOMALIES IDENTIFIABLE FROM COLLAR COUPLINGS AND HAVING A CHARACTERISTIC RADIOACTIVITY ANOMALY; LOGGING THE EARTH FORMATIONS TRAVERSED BY THE FIRST STRING OF TUBING WITH RADIOACTIVITY ANOMALY DETECTING MEANS TO OBTAIN INDICATIONS OF THE RADIOACTIVITY OF THE TRAVERSED EARTH FORMA 